The present invention relates to an optical demodulator used in a multi-channel optical communication system.
Conventionally, an optical demodulator for optical communication generally uses an avalanche photodiode which is capable of high-speed response. The maximum operation frequency of the avalanche photodiode in the response is several tens of GHz.
However, optical communication has the potential for demodulation up to several tens of THz. If the multi-channel capability is not utilized up to the demodulation of several tens of THz, then the advantages of optical communication in which light is used as a carrier are not sufficiently exhibited.
In this connection, the prior art has not sufficiently utilized the advantages of the optical communication, and development of an optical demodulator which operates at a frequency exceeding several tens of GHz has been desired.